To improve joint characteristics by mixing a fiber of a reinforcing material having a function equivalent to that of a base material with a connecting part and forming the connecting part of a composite material in a composite material connecting joint indispensable when a composite structure is built or manufactured at a structure building site at a low cost in a composite material structure using a thermoplastic and thermosetting polymer material as the base material.

Joint characteristics are improved by exposing the fiber of a connecting part by dissolving the base material by incinerating, melting the material at a melting point or higher, dissolving the material in an organic solvent or mechanically removing the material, entangling the fibers with each other, then impregnating the material, again complexing the material and forming the joint.